FM / postinst.d

/etc/kernel/postinst.d

Name	Size	Mode	Actions
initramfs-tools	863	0755	edit dl rm
unattended-upgrades	1163	0755	edit dl rm
update-notifier	1550	0755	edit dl rm
xx-update-initrd-links	882	0755	edit dl rm
zz-shim	372	0755	edit dl rm
zz-update-grub	646	0755	edit dl rm

Edit: /usr/share/update-notifier/notify-reboot-required (1550B)

#!/bin/sh

# we do not include ". gettext.sh" here because:
# a) it breaks if its not available
# b) the string we have here does not need it (because it has no vars)
eval_gettext() {
    if [ -x /usr/bin/gettext ]; then
        echo $(gettext "$1")
    else
        echo "$1"
    fi
}
export TEXTDOMAIN=update-notifier
export TEXTDOMAINDIR=/usr/share/locale

case "$DPKG_MAINTSCRIPT_PACKAGE::$DPKG_MAINTSCRIPT_NAME" in
    linux-image-extra*::postrm)
        exit 0;;
esac

if [ "$0" = "/etc/kernel/postinst.d/update-notifier" ]; then
    DPKG_MAINTSCRIPT_PACKAGE=linux-base
fi

KERNEL_UPGRADED=0
# Prefer showing the canonical-livepatch reboot message if one is required
if [ -f "/snap/bin/canonical-livepatch" ]; then
    # k-u-r returns 1 if livepatch isn't enabled or if a reboot isn't required
    kur_rc=$(/snap/bin/canonical-livepatch kernel-upgrade-required 2> /dev/null)
    if [ $? -eq 0 ]; then
        exit 0;
    elif [ $? -eq 1 ]; then
        # status returns 1 if livepatch isn't enabled
        status_rc=$(/snap/bin/canonical-livepatch status 2> /dev/null)
        if [ $? -eq 0 ]; then
            KERNEL_UPGRADED=1
        fi
    fi
fi

# while a reboot isn't required for the new kernel it might be for another package
if [ $KERNEL_UPGRADED -eq 1 ]; then
    if [ "$(echo $DPKG_MAINTSCRIPT_PACKAGE | cut -c1-5)" = "linux" ]; then
        exit 0;
    fi
fi

# Wake the applet up
echo "*** $(eval_gettext "System restart required") ***" > /var/run/reboot-required
echo "$DPKG_MAINTSCRIPT_PACKAGE" >> /var/run/reboot-required.pkgs

cmd: